In the parent application, a method and apparatus are described for a simple and relatively inexpensive, practical production of photomasks for sandblast engraving or sand carving directly at a user's site. While the structure and method described therein is very effective, it is desirable to be able to effect washing of the uncured emulsion from the stencil utilizing equipment that is somewhat more efficient and/or effective than the open tank with reciprocating spray heads described in the parent application. Heretofore, it has not been considered feasible to utilize a spinning drum washout system utilizing the sophisticated and relatively expensive equipment described in the prior art section of the parent application directly at a use site. However according to the present invention it is possible to produce a relatively simple and inexpensive, yet effective and efficient, spin processor for washing uncured emulsion from a stencil directly at a user's site.
The basic apparatus according to the present invention includes a drum that is mounted for rotation about a horizontal axis, and is driven (e.g. belt driven) with a small electric motor at a relatively slow angular speed (e.g. 50-100 rpm). A high pressure pump is mounted within the same portable cabinet as the drum and motor, and is operated at the same time as the motor to direct liquid (primarily water) through 4-10 V-jet nozzles to provide uniform water distribution over the stencil, and the sprayed water is effectively and simply recycled utilizing a catch basin, a heat insulated holding tank with electrical heating element, and the like.
According to one aspect of the present invention, an apparatus for removing uncured emulsion from a stencil in the production of photomasks is provided. The apparatus comprises the following elements: A drum having an exterior surface for receipt of a stencil thereon. Means for holding a stencil onto the drum exterior surface. Means for mounting the drum for rotation about an axis. An approximately 1/32 to 1/8 horsepower electrical motor for rotating the drum about its axis of rotation. Means for directing streams of high pressure liquid at sufficient temperature, and with sufficient force, and for a sufficient period of time, against a stencil mounted on the drum and rotating therewith to remove uncured emulsion from the stencil. And, control means for controlling operation of the motor.
The apparatus typically further comprises a portable cabinet containing a drum, means mounting the drum for rotation about a horizontal axis, and liquid stream directing means, with an access door being provided to the cabinet (which may be interlocked with the control means). The means for directing streams of liquid typically comprises a high pressure pump (e.g. for pressurizing the liquid to about 80 psi), a plurality of V-jet nozzles, means for collecting liquid running off a stencil mounted on the drum, and conduit means connecting the pump, nozzles, and collecting means for recirculating liquid. The collecting means typically comprises a catch basin mounted below the drum and having a drain therein, and a heat insulated holding tank connected to the drain into the conduit means. An electrical heating element is typically provided in the holding tank for heating collected liquid to an appropriate temperature above ambient (e.g. typically at least about 90.degree. F.). The drain may include a drain pipe having a strainer mounted therein.
Typically the control means controls operation of the motor and substantially simultaneous operation of the pump, and includes a timer and an on/off switch. Most preferably the motor comprises an AC or AC/DC variable speed 1/16 HP motor with a carriage type mounting.
The drum exterior surface is typically of a ferromagnetic material (e.g. galvanized steel) and the stencil holding means comprises a plurality of (e.g. two) magnetic strips, which are on the opposite side of the stencil from the drum. The V-jet nozzles preferably produce flat spray patterns, with uniform water distribution and tapered edges so that the water distribution is uniform even where the spray patterns overlap, and typically 4 to 10 nozzles are provided depending upon the size of the unit. The pump typically comprises an about 1/4-1/2 HP regenerative turbine pump.
According to another aspect of the present invention apparatus for removing uncured emulsion from a stencil in the production of photomasks comprises the following elements: A drum having an exterior surface for receipt of a stencil thereon. Means for holding a stencil onto the drum exterior surface. Means for mounting the drum for rotation about an axis. Means for rotating the drum about its axis of rotation at an angular speed between about 50-100 rpm. Means for directing streams of high pressure liquid at sufficient temperature, and with sufficient force, and for a sufficient period of time, against a stencil mounted on the drum and rotating therewith to remove uncured emulsion from the stencil; the means comprising: a high pressure pump; a plurality of V-jet nozzles; means for collecting liquid running off a stencil mounted on the drum; and conduit means connecting the pump, nozzles, and collecting means for recirculating liquid. And, control means for controlling operation of the motor and the pump.
The invention also contemplates a method of making a photomask having a carrier sheet covered with a cured design structure from a stencil (which itself comprises a carrier sheet with a curable emulsion coating). The method is basically the same as that described in the parent application except for the manner of washing. The method comprises the steps of substantially sequentially: (a) Clamping a stencil in face-to-face contact with a print positive sheet having design elements, the stencil emulsion coating contacting the print positive. (b) Exposing the clamped stencil and print positive to emulsion curing radiation, to cure the emulsion except for areas covered by design elements of the print positive. (c) Separating the stencil from the print positive. (d) Mounting the stencil on the exterior surface of a drum rotatable about a horizontal axis of rotation. (e) Rotating the drum about its axis at an angular speed of between about 50-100 rpm. (f) While the drum is rotating, directing a spray pattern of liquid comprising primarily water, at a temperature of at least about 90.degree. F., at a pressure of roughly about 80 psi, to remove uncured emulsion from the stencil. (g) Catching the liquid sprayed onto the stencil, and recirculating it to a holding tank to be reused as spray liquid in step (f). (h) After steps (e) and (f) have been practiced a sufficient length of time to remove substantially all uncured emulsion, taking the stencil off of the drum. (i) Manually blotting the stencil. (j) Drying the stencil. And, (k) manually applying adhesive to the cured emulsion coating face of the stencil, to produce a photomask. Step (f) is typically practiced to provide 4-10 flat spray patterns with uniform liquid distribution and tapered edges so as to provide uniformity where the spray patterns overlap, and step (g) is further practiced by heating liquid in the holding tank, and heat insulating the tank.
It is the primary object of the present invention to provide a simple, yet efficient and effective, apparatus for washing stencils directly at a user's site during the production of photomasks, and a method of producing such photomasks utilizing an apparatus. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.